1. Field
One embodiment of the invention relates to a storage medium such as an optical disk, a reproducing method, and a recording method of the storage medium.
2. Description of the Related Art
As write-once type optical disks each using an organic dye material for a recording material, there have been commercially available a CD-R disk using a recording/reproducing laser light source with a wavelength of 780 nm and a DVD-R disk using a recording/reproducing laser light source with a wavelength of 650 nm. There has been proposed that a cyanine dye thin film capable of changing physical property with light of a comparatively long wavelength, 790 nm for example, is used for a recording layer (reference should be made to Japanese Patent Application KOKOKU Publication No. 6-43147, for example.)
On the other hand, in principle, density can be increased in inverse proportion to a square of a wavelength of a recording/reproducing laser, and thus, it is desirable that a laser with a shorter wavelength be used for recording/reproduction. In recent years, there has been developed a next generation optical disk which achieves high density. Here, it is assumed that a wavelength of the recording or reproducing laser light source is in the vicinity of 405 nm (namely, in the range of 355 nm to 455 nm). In an organic dye recording material optimized with a light of 650 nm in wavelength, if the light to be used becomes shorter than 620 nm, recording/reproducing characteristics drastically change. Thus, an organic dye material compatible with 620 nm cannot be used as a recording material for a next generation optical disk.
The above document relates to an information storage medium having a recording layer which contains a cyanine dye. It is assumed that a wavelength of a recording laser light source is 780 nm, and recording using a light source with a wavelength of 620 nm or less is not presumed.